Semiconductor integrated circuits of late use miniaturized transistors of low power consumption. To assure operational reliability of these transistors, the power supply voltages used are becoming lower and, to assure a high operating speed of the semiconductor integrated circuit of the low power supply voltage, transistors of low threshold voltages are used in peripheral circuitry. However, if the transistor threshold voltage is lowered, the gate-to-source voltage of the transistor approaches to 0V to increase the current that flows under the transistor off state (off leak current) and hence the standby current of the semiconductor integrated circuit. There has thus been known a technique in which the source potential of a transistor, turned off at the standby time, is connected to a power supply that is turned off at the standby time, thereby reducing the standby current (Patent Document 1).    [Patent Document]    [Patent Document 1]
JP Patent Kokai JP-H11-31385A